By analyzing structure-borne noise it is possible to identify features which assist in the detection of faults or errors in mechanical, electromechanical or fluidic components. For example, EP 1 216 375 B1 discloses a diagnostic system for a valve which can be actuated by a positioner via a drive wherein the intensity of the structure-borne noise in a spectral range above 50 kHz is used for detecting a leakage in the valve. However, the known diagnostic system requires a spectral analysis of the measurement signal and hence involves a substantial overhead in terms of electronics and computing power. It also entails an increase in the electrical power consumption of the evaluation unit. Integration of the diagnostic method as an additional function into existing devices is therefore only rarely possible, since the additional power is often unavailable. This applies in particular to field devices of automation systems, e.g. measurement transformers or final control elements. These must satisfy explosion protection requirements in many cases, or are supplied with the necessary auxiliary energy via a 4 to 20 mA interface or a PROFIBUS connection. The diagnostic system must then be housed in an additional device at additional expense.
Patent specification U.S. Pat. No. 5,477,729 discloses a sensor for structure-borne noise, which sensor is suitable for measuring high-frequency acoustic signals up to approximately 2 MHz.